Centralized Buffer Router with Elastic Links and Bubble Flow Control

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Abstract

While router buffers have been used as performance
multipliers, they are also major consumers of area and power in
on-chip networks. In this paper, we propose centralized elastic
bubble router - a router micro-architecture based on the use of
centralized buffers (CB) with elastic buffered (EB) links. At low
loads, the CB is power gated, bypassed, and optimized to produce
single cycle operation. A novel extension to bubble flow control
enables routing deadlock and message dependent deadlock to be
avoided with the same mechanism having constant buffer size per
router independent of the number of message types. This solution
enables end-to-end latency reduction via high radix switches with
low overall buffer requirements. Comparisons made with other
low latency routers across different topologies show consistent
performance improvement, for example 26% improvement in no
load latency of a 2D Mesh and 4X improvement in saturation
throughput in a 2D-Generalized Hypercube.